In general, magnetic recording media such as flexible magnetic discs or magnetic sheets can be prepared by coating a non-magnetic support (e.g., polyethylene terephthalate, cellulose triacetate, cellulose diacetate, poly(vinylidene chloride) or polypropylene) which is in the form of strip and is continuously travelling in the machine direction with a coating composition containing ferromagnetic fine particles (e.g., .gamma.-Fe.sub.2 O.sub.3, Fe.sub.3 O.sub.4, Co-doped .gamma.-Fe.sub.2 O.sub.3, Co-doped .gamma.-Fe.sub.3 O.sub.4 or CrO.sub.2) dispersed in a solvent solution of a binder (e.g., a vinyl chloride-vinyl acetate copolymer, a vinyl chloride-acrylonitrile copolymer, an acrylic acid ester-acrylonitrile copolymer, an acrylic acid ester-vinylidene chloride copolymer, an acrylic acid copolymer, a urethane elastomer, a nylon-silicone type copolymer, nitrocellulose, polyvinyl chloride, a vinylidene chloride-acrylonitrile copolymer, a polyamide resin, polyvinyl butyral, cellulose derivatives, a styrene-butadiene copolymer, a phenol resin, an epoxy resin, polyurethane, a urea resin, a melamine resin, a polyester resin, a chlorovinyl etheracrylic acid ester copolymer, a blend polymer of methacrylate copolymer and diisocyanate, an amino resin or a synthetic rubber) by a conventional coating method such as top-reverse coating method, bottom-reverse coating method, doctor coating method or gravure coating method, and drying the coating layer. When ferromagnetic fine particles are arranged in a particular direction during the manufacturing steps of the magnetic recording medium, anisotropy occurs in the magnetic recording medium, and as a result, anisotropy occurs in magnetic properties and electromagnetic properties in various directions.
When a magnetic recording medium in which magnetic particles have been arranged in the coating or machine direction is used as a magnetic disc, the output level of the reproduced signal in the coating direction is higher than that in other directions, and as a result, the output signal level reproduced by rotating magnetic discs changes depending upon the position of the magnetic discs where the signal is recorded. This phenomenon is referred to as modulation. Therefore, flexible magnetic discs which are used for recording and reproducing by rotation have been conventionally prepared while physically removing orientation of magnetic particles or while excluding a magnetic field during the production of magnetic recording tapes so that the ferromagnetic fine particles are not arranged in the linear direction. However, even if the above particular means is applied, there is a problem in that magnetic particles are arranged in the coating direction by orientation due to the flow of the coating composition and, as a result, the output level of the reproduced signals changes depending upon the position of the discs.
In order to eliminate orientation caused by the flow of the coating composition which is caused immediately after coating, it is proposed in Japanese Patent Publication (Unexamined) Nos. 104,205/78 and 149,607/79 that the magnetic coating layer be subjected to magnetic orientation to one direction in a first magnetic field for orientation and then be subjected to magnetic orientation in a second magnetic field for orientation which is weaker than the first magnetic field, with the direction of orientation of the second field being the reverse of the first field.
However, according to the method and apparatus as proposed in the above Japanese patent publications, random orientation can not be sufficiently attained because random orientation treatment disclosed in these prior arts is conducted intermittently and is completed in a short period of time since this conventional process uses the independent lines of the magnetic field caused by each magnetic field for orientation and uses only first and second magnetic fields for orientation.